Accident Sequence
During final approach to a rooftop helipad, approximately 15 feet above the pad, the helicopter's controls became very stiff. The pilot observed the "HYD" caution light illuminated on the panel, but the audible hydraulic warning horn did not activate. Subsequently, the helicopter contacted the helipad with the right skid and rolled onto its right side.
Post-Accident Examination
Examination of the cockpit revealed that the hydraulic cut-off switch, located on the collective control, was found in the cut-off position. Its red plastic guard was broken; when the switch is in the cut-off position, the hydraulic warning horn does not sound. The cockpit was searched for shattered pieces of the guard, but none were found.
Hydraulic System Findings
Inspection of the hydraulic system showed no leaks. A functional test of the hydraulic pump and regulator/manifold revealed no anomalies with either unit.